The Collaborative International Dictionary of English v.0.48:

Undulatory \Un"du*la*to*ry\ (?; 277), a. [Cf. F. ondulatoire.]
   Moving in the manner of undulations, or waves; resembling the
   motion of waves, which successively rise or swell rise or
   swell and fall; pertaining to a propagated alternating
   motion, similar to that of waves.
   [1913 Webster]

   Undulatory theory, or Wave theory (of light) (Opt.), that
      theory which regards the various phenomena of light as due
      to undulations in an ethereal medium, propagated from the
      radiant with immense, but measurable, velocities, and
      producing different impressions on the retina according to
      their amplitude and frequency, the sensation of brightness
      depending on the former, that of color on the latter. The
      undulations are supposed to take place, not in the
      direction of propagation, as in the air waves constituting
      sound, but transversely, and the various phenomena of
      refraction, polarization, interference, etc., are
      attributable to the different affections of these
      undulations in different circumstances of propagation. It
      is computed that the frequency of the undulations
      corresponding to the several colors of the spectrum ranges
      from 458 millions of millions per second for the extreme
      red ray, to 727 millions of millions for the extreme
      violet, and their lengths for the same colors, from the
      thirty-eight thousandth to the sixty thousandth part of an
      inch. The theory of ethereal undulations is applicable not
      only to the phenomena of light, but also to those of heat.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wave \Wave\, n. [From Wave, v.; not the same word as OE. wawe,
   waghe, a wave, which is akin to E. wag to move. [root]138.
   See Wave, v. i.]
   [1913 Webster]
   1. An advancing ridge or swell on the surface of a liquid, as
      of the sea, resulting from the oscillatory motion of the
      particles composing it when disturbed by any force their
      position of rest; an undulation.
      [1913 Webster]

            The wave behind impels the wave before. --Pope.
      [1913 Webster]

   2. (Physics) A vibration propagated from particle to particle
      through a body or elastic medium, as in the transmission
      of sound; an assemblage of vibrating molecules in all
      phases of a vibration, with no phase repeated; a wave of
      vibration; an undulation. See Undulation.
      [1913 Webster]

   3. Water; a body of water. [Poetic] "Deep drank Lord Marmion
      of the wave." --Sir W. Scott.
      [1913 Webster]

            Build a ship to save thee from the flood,
            I 'll furnish thee with fresh wave, bread, and wine.
                                                  --Chapman.
      [1913 Webster]

   4. Unevenness; inequality of surface. --Sir I. Newton.
      [1913 Webster]

   5. A waving or undulating motion; a signal made with the
      hand, a flag, etc.
      [1913 Webster]

   6. The undulating line or streak of luster on cloth watered,
      or calendered, or on damask steel.
      [1913 Webster]

   7. Something resembling or likened to a water wave, as in
      rising unusually high, in being of unusual extent, or in
      progressive motion; a swelling or excitement, as of
      feeling or energy; a tide; flood; period of intensity,
      usual activity, or the like; as, a wave of enthusiasm;
      waves of applause.
      [Webster 1913 Suppl.]

   Wave front (Physics), the surface of initial displacement
      of the particles in a medium, as a wave of vibration
      advances.

   Wave length (Physics), the space, reckoned in the direction
      of propagation, occupied by a complete wave or undulation,
      as of light, sound, etc.; the distance from a point or
      phase in a wave to the nearest point at which the same
      phase occurs.

   Wave line (Shipbuilding), a line of a vessel's hull, shaped
      in accordance with the wave-line system.

   Wave-line system, Wave-line theory (Shipbuilding), a
      system or theory of designing the lines of a vessel, which
      takes into consideration the length and shape of a wave
      which travels at a certain speed.

   Wave loaf, a loaf for a wave offering. --Lev. viii. 27.

   Wave moth (Zool.), any one of numerous species of small
      geometrid moths belonging to Acidalia and allied genera;
      -- so called from the wavelike color markings on the
      wings.

   Wave offering, an offering made in the Jewish services by
      waving the object, as a loaf of bread, toward the four
      cardinal points. --Num. xviii. 11.

   Wave of vibration (Physics), a wave which consists in, or
      is occasioned by, the production and transmission of a
      vibratory state from particle to particle through a body.


   Wave surface.
      (a) (Physics) A surface of simultaneous and equal
          displacement of the particles composing a wave of
          vibration.
      (b) (Geom.) A mathematical surface of the fourth order
          which, upon certain hypotheses, is the locus of a wave
          surface of light in the interior of crystals. It is
          used in explaining the phenomena of double refraction.
          See under Refraction.

   Wave theory. (Physics) See Undulatory theory, under
      Undulatory.
      [1913 Webster]

WordNet (r) 3.0 (2006):

wave theory
    n 1: (physics) the theory that light is transmitted as waves
         [syn: wave theory, undulatory theory, wave theory of
         light] [ant: corpuscular theory, corpuscular theory of
         light]